Rename SkTDArray::rewind -> clear

Change-Id: I807a52b0c3c0076c81be8f5b201e640def7ca8ac
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/586437
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Herb Derby <herb@google.com>
12 files changed